Scanf.scanf "%d" (fun n ->
    let a = Array.init n (fun _ -> Scanf.scanf " %d" (fun a -> a)) in
    let ao = Array.fold_left (lor) 0 a in

    let rec loop i =
        if i land ao = 0 then i else loop (i * 2)
    in
    loop 1 |> Printf.printf "%d\n"
)